The present invention relates in general to solid chemical dispensing systems, and in particular to various embodiments of solid chemical dispensing systems that include multiple vessels used to dispense chemical solutions.
Generally, solid chemical dispensing systems are used to add chemicals to minimize and/or inhibit corrosion in boiler systems, cooling towers, fluid processing systems, etc. Such solid chemical dispensing systems generally employ vessels that contain a dissolvable solid chemical that is mixed with a fluid, such as water, to form a corrosion inhibiting/prevention solution. Typically, the vessels have an output conduit used for dispensing the solution into a holding reservoir, or directly into fluid processing systems.
Conventional solid chemical dispensing systems often use water under pressure that is sprayed into a vessel containing a dissolvable solid chemical. The force of the water, and agitation, mix the chemical with the water inside the vessel to form the solution. While, conventional solid chemical dispensing systems have proven effective in providing solutions that reduce the amount of corrosion in boilers, cooling towers, etc., the solution's effectiveness is dramatically reduced when the dissolvable solid chemical is depleted. Once the dissolvable solid chemical in a vessel is completely dissolved, the dissolvable solid chemical is replaced, or another vessel containing dissolvable solid chemical is used in its place.
The chemical dispensing industry has provided multi-vessel solid chemical dispensing systems to help resolve the depletion problem. Such multi-vessel solid chemical dispensing systems provide switching between vessels to maintain the solution concentration. For some conventional multi-vessel solid chemical dispensing systems, when a vessel in use is depleted of its dissolvable solid chemical, a controller automatically switches to another vessel containing dissolvable solid chemical. In order to determine when to switch between vessels, conventional multi-vessel systems measure conductivity in a reservoir or sump holding the solution. As the conductivity of the solution in the reservoir changes with respect to the amount of dissolvable solid chemical remaining, the multi-vessel system switches between vessels when the conductivity measurement in the reservoir reaches a predetermined conductivity threshold.
Unfortunately, such conventional multi-vessel systems that measure conductivity in the reservoir as a guide, measure the conductivity against a predefined set point value without regard to the change in conductivity in the water used to create the solution. As conductivity may dramatically change between different sources of water, solution concentrations may vary, and therefore the effectiveness of the conventional multi-vessel systems may vary as well.
Therefore, what is needed is a multi-vessel solid chemical dispensing system that provides a consistent and uniform solution concentration that is easy to use and integrate into fluid systems.